Backup systems provide backup storage to remote host computers. A conventional backup system includes multiple backup servers, each of which contains storage disks on which host data is backed up. Some backup systems also include a broker computer that selects backup servers on which to store arriving data. For example, a broker computer may perform load balancing operations, such as for balancing the amount of data stored on each backup server, managing network traffic, and avoiding hot spots. In such a backup system, when a host computer sends backup data to the backup system, the broker computer steers the backup data to a backup server that has available storage space and bandwidth.
Some backup servers perform deduplication on backup data. Such deduplication involves a backup server searching backed up data on its storage devices for redundant data blocks. Upon finding a redundant block, deduplication replaces the redundant block with a pointer to a remaining block that contains the common data. As is known, a “block” is a logical unit of storage, such as 4 KB, 8 KB, or some other size, which is generally the smallest unit of storage that a file system can allocate and manage.